Significance and importance of culture of microorganisms, and production of substances by microorganisms (fermentative production, bioconversion, etc.) are increasingly growing on the basis of increasing concerns for environmental issues, food issues, health and safety, as well as elevation of orientation for native or nature, and the like.
In culture of a microorganism and production of a substance by a microorganism, a carbon source suitably utilized by the microorganism (carbon source for culture, fermentation, etc.) is required. Typical examples of the carbon source include carbohydrate, fats and oils, short chain fatty acids, and the like.
In recent years, regenerable carbon sources (in particular, nonpetroleum-derived carbon source), and more preferably carbon sources that do not compete with food (non-edible carbon sources, generally referred to) have been increasingly demanded as carbon sources, on the basis of environmental issues and the like.
In this respect, long chain fatty acids (for example, long chain fatty acids derived from plants) are deemed to be a candidate for suitable carbon sources. Long chain fatty acids can be obtained from, for example, coconut, palm (including palm kernel), and the like. Plants such as coconut and palm have been known to include long chain fatty acids as constitutive fatty acids in fats and oils. Typical long chain fatty acids derived from these plants may include long chain saturated fatty acids such as lauric acid having 12 carbon atoms, myristic acid having 14 carbon atoms and palmitic acid having 16 carbon atoms, and long chain unsaturated fatty acids such as oleic acid having 18 carbon atoms.
These long chain fatty acids have been used as an industrial basic ingredient of surfactants, soaps, cosmetics and the like. However, they have not been widely used in industry that uses microorganisms. In particular, researches on use of these long chain fatty acids as a carbon source for culture of microorganisms and production of substances by microorganisms have not been sufficiently advanced.
Examples of producing PHA using lauric acid or oleic acid alone as a carbon source by culturing Aeromonas hydrophila were reported (see Nonpatent Document 1). However, examples in which oleic acid was used alone as a carbon source were principally investigated, and myristic acid and palmitic acid were not studied.
Although examples of producing PHA using lauric acid or myristic acid alone as a carbon source by culturing Ralstonia eutropha (see Patent Document 1) were reported, the amount of production of PHA is extremely low, not greater than 1 g/L. Also, palmitic acid was not used.
Moreover, examples of producing PHA using a salt such as sodium laurate alone as a carbon source by culturing Escherichia coli (see Nonpatent Document 2) were reported. However, myristic acid and palmitic acid were not used.
In the aforementioned researches, applicable culture scale remains within a small scale ranging several ml to several L.
As in the foregoing, there have been no prospects for possibility of industrially suitably using a variety of long chain fatty acids as a carbon source for culture of microorganisms and production of substances by microorganisms.